Telegraph and telephone receiving system.



L. DE FOREST- TELEGRAPH AND TELEPHONE RECEIVING SYSTEM.

APPLICATION FILED SEPT. 27. 1915.

1,201,272. Patented 001*... 17,1916.

UNITED STATES PATENT OFFICE.

LEE ma FOREST, OF NEW YORK, N. Y., ASSIGNOR TO DE FOREST RADIO TELEPHONE AND TELEGRAPH COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

TELEGRAPH AND TELEPHONE RECEIVING SYSTEM.

Specification of Letters Patent.

Patented Oct. 17, 1916.

To all whom it may concern Be it known that I, LEE on FOREST, a citizen of the United States, residing at New York, county of Bronx, State of New York, have made a certain new and useful invention in Telegraph and Telephone Receiving Systems, of which the following is a specification.

This invention relates to telegraph and telephone receiving systems.

The object of the invention is to provide a receiving system for use in telegraph or telephone communication systems which is simple and eflicient.

Further objects of the invention will appear more fully hereinafter.

The invention consists substantially in the construction, combination, location and circuit arrangement all as will be more fully hereinafter set forth, as shown by the accompanying drawing, and finally pointed out in the appended claims.

Referring to the drawing, the single figure shows a diagrammatic wiring arrangement embodying my invention.

In the present use of audion detectors employing the usual wing, grid and filament electrodes, it has been considered a disadvantage to employ a battery as a source of electromotive force in the filament, tele phone and plate circuit of a receiving system, in that the battery frequently needs renewal. This is especially true in tropical climates, as I have found that cells, especially dry cells, quickly run down and deteriorate. Heretofore it has been impractical to employ a dynamo or direct current mains to take the place of this battery for the reason that, as a general rule, the noise in the telephone receiver from the commutator of the generator supplying the mains is many times louder than the sound of the received signals. Moreover, there are usually present, from such power mains, loud induction noises which also render the audion too insensitive'as a detector of feeble impulses.

It is among the special purposes of my present invention to render it possible to use a dynamo or large current supply mains in the wing circuit of the audion in a signal receiving system.

In the drawing, 17 and 18, designate positive and negative terminals which may be connected, as hereinbefore explained, to a generator or to large direct current supply means. In each of the leads of the terminals 17, 18, I provide choke coils 1, 2, preferably wound around iron cores, as shown. Connected across the leads of the terminals 1s a condenser 3 of from 1 to 2 miorofarads capaclty.

Reference numeral 4 designates a high resistancepotentiometer, preferably of from 5,000 to 25,000, ohms resistance also connected across the mains, as shown. The potentiometer may be of any desired charactor. I have found it sufficient to employ a graphite rod, but I am not to be limited in this respect. The potentiometer is provided with the usual sliding contact indicated at 5, to cut in or out the resistance of the rod. I prefer to connect a condenser 6 across the portion of the potentiometer included between the main 18 and the contact 5. The

sliding contact 5 is connected to the wing electrode 9 of the audion 8 by a suitable circuit including therein the telephone re-- ceiver 7, which may be the usual two drum headpiece. The filament 11 of the audion 8 is provided with the usual heating source, such as battery 12, and the controlling resistance 13 therefor.

Reference numerals 14 and 15, designate the usual capacity and inductance of the circuit included in the secondary coil of the receiving transformer and connecting the grid electrode 10 and the filament electrode 11, as shown.

It will be understood that an audion employed as a detector in an arrangement embodying my invention may be used as a detector of spark signals, as an ultraaudion detector of undamped signals, or as an amplifier of pulsating electric currents of any nature or frequency, as the operation of the current supply means from a generator is the same in each case.

I have found it advantageous to connect directly to earth one side of the receiver circuit through the condenser 6 as at E.

The incoming signals are received by the primary coil 16 of the transformer in the usual well known manner, either from wires, as in wire communications or from an antenna earth system as in radio communications.

The object of the choke coils, and the condenser 3, and potentiometer, as shown, is to weed out the inductive disturbances in the current supply lines, and it is obvious that one of the choke coils or the condenser or both of them may be omitted, if desired, according to how serious the disturbances are.

While I have termed the disturbances which occur in the mains, inductive disturbances, I wish it to be understood that such term will include all disturbances to which power supply mains are subjected.

Modifications of the exact circuit arrangement shown will readily occur to those skilled in the art without departing from the broad scope of my invention as defined in the claims, therefore,

Having set forth the objects and nature of my invention, what I claim as new and useful and of my own invention and desire to secure by Letters Patent, is,

1. In a signal receiving system, the combination with an audion, of power supply mains associated therewith, and means including a condenser and a potentiometer connected across said mains for eliminating the effect of the inductive disturbances in said mains upon said audion.

2. In a signal receiving system, the combination with an audion, of power supply mains associated therewith, and means including a choke coil included in circuit with each of said mains and a condenser connected across said mains for eliminating the effect of the inductive disturbances in said mains upon said audion.

3. In a signal receiving system, the combination with an audion, of power supply mains associated therewith, and means including a choke coil included in the circuit of each of said means and a condenser and potentiometer connected across said mains for eliminating the eifect of the inductive disturbances in said mains upon said audion.

4. In a signal receiving system, the combination with an audion, of power supply mains associated therewith, and means including a capacity and a potentiometer connected across said mains for eliminating the effect of the inductive disturbances in said mains upon said audion.

In testimony whereof I have hereunto set my hand in the presence of the subscribing witnesses, on this th day of September LEE DE FOREST. Witnesses:

S. E. DARBY, J r., M. A. GRAEVE. 

